Warning: The following history includes themes of religion in a negative light, exorcism and death. Read at your own discretion.
Connor and Isobel Thayne had always dreamt of being the patriarch and matriarch to a grand family, one that would stick in the minds of those who lived around them. Some in their town liked to joke that Isobel was inspired by Queen Victoria being the 'Grandmother of Europe' and wanted to become the 'grandmother' of the town. Most others assumed that the two had decided early on into their relationship that it was the goal they wanted to achieve, more so than any career aspirations. The muggle couple did well, birthing six children in quick succession to one another. Accompanying the births of Macauley, Annella, Leith, Maidie, Morag and Ailsa came the notoriety that the two had sought for years; for however older their children got, their names spread across the town and people became interested in the Thayne's as if they were a spectacle of sorts. Their band of six kids brought a sense of comfortableness to Connor and Isobel, enough that any talk of expanding the family further was brushed away as unneeded; useless. A shock pregnancy, however, when Isobel was in her early-forties forced the couple to change their minds. Whilst six had been the ideal number, they'd never say no to a seventh kid - much less an eighth when it was revealed that they were with twins.
Abernathy and Angus rounded up the harem of Thayne children and the perfect family grew to be a little more perfect. Both Connor and Isobel were over the moon; their reach on the families of the town extended further with the birth of their final sons, even more so with the age gap of some thirteen years between them and Ailsa, the previous youngest child. Unbeknown to the Thayne family, however, the youngest Thayne children would always be a little... different. Whilst most of the Thayne's had gone without it, Abernathy and Angus inherited the magical blood that came from Donnchadh Thayne, a fifteenth century magical relative who was heralded as one of the best wizards in Scotland. It would be with no doubt that the twins would be powerful wizards and, had they been in another other family, they would've been seen as impressive and prides to the family, however, they were born at a time where the Thayne family view on magic had been clouded with an extreme, single-minded view on Catholicism. Little did they know as they had small bursts of magic during their infant stage of life, magic that wowed their small minds, that they'd be the bane of their family's existence and shunned away.
However powerful the twins were said to be, however, their initial magic was always small stuff that could be disproved easily through commonsense, logic - probably what made the revelation in years to come all the more shocking for the Thayne family. Small things like doors and windows slamming shut constituted a lot of their early magic with random dips in temperatures whenever the twins' moods changed. Both Connor and Isobel brushed this off as the locale of their village and the rise in winds - nothing to worry about. As they got older and as their parents left them alone in their cribs more, more inexpiable things occurred; toys from the shelves on the opposite side of the room to them would find their way into their cribs and their musical toys such as xylophones would play soothing melodies when it was known that the boys were asleep and unable to get out of their cribs. Connor and Isobel chose to believe it was the work of ghosts and had the local priest clean their house of all dark energy, believing themselves to be content. Needless to say as the instances continued on, they became increasingly fearful.
Up until the age of five, Abernathy and Angus' magic had gone unnoticed or ignored by their parents, but with their first proper magical experience happening just days after their fifth birthday, it became indisputable that it had been them all along doing all the strange things. During a family barbecue with all of their siblings over, Abernathy and Angus had been left to play in the small pool that their parents had set up in the garden for them to entertain themselves with. All seemed well until the sun was eclipse slightly by the sight of water. One glance in the twins' direction would reveal the two manipulating the water to get bigger and bigger. Though unbelievable - hellishly stupid, as Isobel had described it - it was undeniable that they were responsible for it. Though startling and distracting the twins made the whole thing stop, that day would be the last that anyone in the Thayne family would have time for them.
It was only a few days after their first proper magical experience that Connor and Isobel had the twins exorcised for the first time of many. It was a scene with both twins crying as it happened, enough that nearly made their parents believe that they were innocent but it was the stern talking of their eldest siblings who pointedly reminded Connor and Isobel what had happened a few days ago in the past that led them to go through with it. That same night the twins had their bedroom moved to the attic and it was stripped of it's former glory. The endless amounts of toys had been replaced with two or three dull ones; the colour of their walls went from a soft blue to grey and the plush carpet the two had once loved to fall on had been replaced with a floor that was prone to giving them nasty splinters. From then on the boys were also treated with the premise of being handled as little as possible; countless nights the boys cried themselves to sleep for attention and were constantly placed down when they wanted affection. At first, Connor and Isobel were against it but cited it as a necessary course of action to take to expel the demons from their youngest children.
Needless to say, as the boys continued to show signs of magic in the form of multiplying their toys and shattering the singular window in their room even after the exorcism, the love their family felt towards them diminished even further and was increasingly replaced by a stone cold fear. The exorcisms the two went through became weekly and, as magic continued to prevail, biweekly. Angus was always more willing to work during the exorcisms, having calmed down over time whilst Abernathy still resisted. This led to them being known as 'the Gemini' within their family, so much so that it was only the twins themselves who called each other by their first names. As mentioned, if they had been born into any other incarnation of the Thayne family, Abernathy and Angus would be heralded as the premature beginnings of greatness and would be spoiled with a pre-Hogwarts wizarding education second to none but, instead, the two were home schooled and rarely let out of the attic that they slept in.
It didn't take long for the twins existence, which had once been heralded as a celebration of the Thayne's further goal of populating the town, to become a rumour. Their neighbours were no longer sure if there had been two extra boys born and a scepticism surrounding Connor and Isobel formed, with some going as far as to claim that Connor had murdered them. In reality, Abernathy and Angus were left up in the attic, rarely being allowed to go down to the second floor of the house to have some breathing time. Though they were harsh with what they did, Connor and Isobel were conscious that if they treated their children so abhorrently that it'd come back around. For them, however, they thought that some breathing room on the second floor - not even the garden - was enough to satisfy their sons' need for a meaningful life. Needless to say that Abernathy and Angus, although young, had other ideas.
The exorcisms the two were put through became triweekly as their magic seemed as ever prevalent, right up until they got their letters of acceptance to Hogwarts. At first, Connor and Isobel were hesitant. The simple fact that there was a whole school for people like their demon children unnerved them - thankfully they never learnt about it's Scottish home - and that in itself was grounds for them to go. That is, until they figured out that if their sons were 'wizards' then them learning how to hone their abilities would stop the random bursts of magic around them and, in turn, the exorcisms. Moreover, they believed that with their sons up away somewhere for the majority of the year meant that they could breathe again. Through a family meeting without Abernathy and Angus - though they knew of Hogwarts thanks to some letters finding their way up to the attic - the Thayne's decided that the twins would go there to learn their powers and prevail.
To say that the twins were excited to be leaving the home was, by far, an understatement. The two were elated at the prospect and it was the only thing they talked about between themselves; alongside how much contempt they had for their parents but that conversation was old. Hogwarts was new and they couldn't wait to immerse themselves fully into everything it had to offer. Seeing as the two were the first magical Thayne's in some years, the two were given a vault to access in Gringotts. There wasn't a lot there, but enough for them to use to buy their supplies and ration out throughout the years. The two were never once accompanied by their family - though their most sympathetic sister, Maidie, did take them down to London so they could go to Diagon Alley. The twins bought all of their supplies and promptly had them sent to Hogwarts before they themselves would go down a few days later.
The goodbyes were non existent at the Thayne house; as soon as the boys had visited London that day a few days before their actual leaving date, their parents began to change the attic to a more positive space - clearly showing the two that they had little room in the house for them. At this point, however, there was little care on Abernathy and Angus' side; they both wanted out as soon as possible and rejoiced the night before. Without saying any good wishes, goodbyes or anything of the like, Abernathy and Angus went down to King's Cross station, ready to begin the journey to their new home, their new lives. Upon reaching Hogwarts, Abernathy and Angus were sorted into Ravenclaw and Gryffindor respectively. Though they immersed themselves with their new housemates and threw themselves into wizarding life, the two were still joined at the hip whenever they could be, enabling the two of them to be recognised easily.
The two were quite proficient with magic, living up to their early magical experiences and their Thayne name. Both had an apt for spells over other aspects of magic, but it was undeniable that they were decent well rounded wizards with the potential to be great. The two fell in love with the life enough that, over the years, they tried their best to not go home as much as they could. The only time they left Hogwarts was over the summer and, even then, the two rarely returned home. They found that their parents warmed up to them a little - though, in the grand scheme of things, that wasn't much to boast about - as they now had their powers under control but, still, they felt like they were loathed and the abuse they endured became more psychological and subtle. Instead, the boys would live around the country with their various schoolmates. Though Scotland was their preferred place - understanding the accent contributed to that - they found that they enjoyed the south of England for temperature that was warm enough to enjoy the beaches. Plus both of them felt they had an attachment to water, seeing as water had been the cause of this whole shift in their life.
When the two graduated Hogwarts at eighteen with impressive results, they found that was where their lives changed even further. You see, as they got older the abuse they endured became worse, just not on the outside. Whereas before people could tell if the boys were being mistreated, now it had become invisible, so much so that the two confided in one another to try and make sense of what had happened and feel confident in the decision that they hadn't made whatever happened to them up. Contempt for their parents grew between them but both had different ways of dealing with it. Angus, the one who had cooperated with exorcisms on the account of just wanting a normal life, was more into writing things down and forgiving and forgetting. He could hold a grudge but he enjoyed getting to the root of it. Abernathy, the one who always violently refused during the exorcisms, was a lot louder - a lot more comically mad. Schoolmates could understand why their family called them 'The Gemini' whenever the twins got angry. The event in question happened when the two returned home to collect their things. To their horror, they walked in on their family burning their possessions. Caught in the act, the family screamed at them and called them names like 'devils' and 'demons.' It was clear that they wanted nothing to do with them and that was how their reactions differed. In a rage, Abernathy's blindsided anger took over and soon water began filling the house, forcing their parents and siblings to flee up to the attic in an attempt to save themselves. Angus, not noticing until the entirety of the first floor was flooded, got his own wand out to try and reverse the spell that Abernathy was using. Whether it was down to the foreshadowing bad weather and the two being outside or fighting against Abernathy's determination, Angus was unable to put a stop to the rising water levels and soon after the two were orphaned.
The two immediately left the scene and returned to the wizarding world, keeping the secret with them. Abernathy had forced Angus to promise that he wouldn't tell anyone and, for the most part, Angus intended not to. For all his life Abernathy had been the only constant and he didn't want to lose him. It wasn't long, however, until the Ministry began to question the two as muggles had, ultimately, died at the hands of wizards. At first, Angus refused to give up any knowledge and it looked like the two of them were to be sent to Azkaban until he cracked. Though he swears he was under the truth serum, Angus recollected the events perfectly and exposed Abernathy as the main driving force of their family's death whilst he was doing all he could to stop it. Subsequently, Angus was given a payment for his cooperation whilst Abernathy got time in Azkaban. Angus never saw his twin after the first day they were taken to the Ministry for questioning and he felt guilty upon being given the large sum of money, knowing that it was all down to him ratting out his brother despite the promise he had made.
For the first few months after the incident, Angus continued to live with various schoolmates whilst he did small jobs here and there. A paper boy for The Daily Prophet; a barman at The Leaky Cauldron - menial jobs. Eventually he got a one bedroom flat in Diagon Alley, choosing to base himself there for the majority of his young adult life. In all truth, Angus felt lost without his brother. Having been attached to the hip with him for the first eighteen years of his life meant that Angus felt empty without him. Though he knew that the likelihood of Abernathy wanting any relation with him - despite the Aurors telling him that they'd make sure Abernathy would continue to think that Angus had kept his secret - was slim, Angus couldn't help but pine for his brother.
It was during this period of his life, from when he was nineteen to about twenty-three, that he gained a reputation for having a laissez-faire attitude towards everything.